The invention relates to the packaging of aromatic food products. Specifically, the invention is directed to an improved laminate for coffee packaging.
Packaging coffee and other aromatic materials in containers formed from laminates is known. The laminates used for coffee packaging are designed to minimize the transmission of oxygen, moisture and aromas. Conventional coffee packaging has done a generally good job at keeping coffee fresh and free of unwanted contaminants. Such coffee packaging generally is formed from a sheet of metal foil, various layers of known plastics, and adhesives. A conventional coffee package may have a laminate structure (from inner layer to outer layer) of: polyethylene (PE); biaxially oriented nylon (BON) or inner polyethylene terephthalate (PET); metal foil; and outer polyester, such as PET. A printed ink layer is often reverse printed on the PET layer. U.S. Pat. No. 5,352,466 to Delonis discloses a coffee package which may be formed from a laminate having this general structure.
U.S. Pat. No. 5,250,334 to Lutterotti discloses another laminate for coffee packaging. Lutterotti shows that a metallized layer can be used in place of a foil layer in coffee packaging. In conventional metallized structures, the metallization is deposited onto a substrate of either biaxially oriented polyethylene terephthalate (PET) or biaxially oriented polypropylene (OPP). In one known structure the opposite surface of the PET is coated with saran to provide a heat seal layer. In another known structure, a film of PET and PETG (glycol modified polyethylene terephthalate) is metallized on the surface of the oriented PET layer. In that structure the PETG serves as the sealant layer. In both of the above structures, the metallized surface (and sometimes intervening layers) is then laminated to an abuse resistant layer such as OPP or oriented PET.
The need for an abuse resistant layer is a problem with conventional coffee packaging. An outer web (often PET or OPP), and an adhesive for bonding the web, are required to protect the ink layer from scrapes and abuse. This outer web not only is expensive in the material cost of adhesive and resin, but also in the extra manufacturing step of laminating the outer web onto the laminate.
Another problem with many laminates is the migration of slip agents. Coffee packaging is no exception. Slip agents are commonly added to laminates to enhance the processing thereof. The slip agents reduce the coefficient of friction of the laminate as measured against itself and against machine parts across which the laminate may slide. The decreased coefficient of friction allows the laminate to be easily moved across such surfaces without ripping or wrinkling. However, slip agents are prone to migration which can cause delamination of the laminate as well as interference with adhesion of metal layers and the like.
The inventors of the subject matter described herein have used great skill and effort to find that certain energy curable coatings can be used to protect the ink layer in coffee packaging. This advance not only allows for the elimination of the manufacturing expenses associated with the outer polymer web and the adhesive associated therewith, but also solves the long hexing problem of slip agent migration. Energy curable coatings generally come in two forms, electron beam (EB) curable coatings, and ultra violet (UV) curable coatings. One example of an energy cured coating is disclosed in U.S. Pat. No. 4,654,379 to Lapin which describes a semi-interpenetrating polymer network.
The present invention is directed to a new laminate which is especially well suited for coffee packaging. The laminate comprises a strength layer, an inorganic layer, and an energy curable layer. Preferably an ink layer is also provided, disposed between the energy curable layer and the strength layer. It is also preferable to provide a sealant layer.
The energy curable layer includes slip agents. The slip agents become xe2x80x9creacted-inxe2x80x9d during crosslinking (curing) of the layer. Thus, the slip agents are fixed or, in other words, are non-migratory.
Further, the laminate of the present invention is more economical to produce than a conventional laminate for coffee packaging. Production of a laminate according to the present invention requires fewer raw materials than does a conventional coffee packaging laminate. In addition, the laminate of the present invention may be manufactured in fewer manufacturing steps.